An extended version of our paper "Analytic Model for SDN Controller Traffic and Switch Table Occupancy" will be published in the next issue of the IEEE Transactions on Network and Service Management.

Abstract:

Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

We begin a new Master's thesis on the topic "Evaluating Multiple Impact Factors on the Reconvergence of SDN". The topic will help us in our SDN RAS² project and gives us important insights into the performance of current SDN controllers.

Our new Project "SDN-RAS²" has been started today. This project focuses on Fast failure Detection in Software-Defined Networks and is a successor to our "SDN-RAS" project. We are looking forward to continue the cooperation with our partner.

Summary

The need to more flexibility in the management and control of today’s networks led to the development of new networking paradigms like Software-Defined Networking (SDN) and Network Function Virtualization (NFV). The SDN paradigm introduces a more flexible control of networks by separating the network control and data plane, and logically centralizing the control plane on the so-called SDN controller. The interaction between control and data plane is typically realized by a communication using a standardized protocol like OpenFlow.

The application of this SDN paradigm in operational networks assumes that the reliability and availability is ensured. For today’s network operators, this is one of the most important criteria when introducing SDN. To this end, therefore, sophisticated measures and innovative mechanisms are needed to ensure the required reliability and availability.

A recent idea in this context is based the following saying: “Fail fast is more important than fail-safe”. This means, it is more important to detect errors quickly than to build a system that is 100% accurate and faultless. The latter is de-facto not possible in an operational system, which constantly changes and receives updates. For such an approach enhanced analytics of the network including its devices is a mandatory requirement as it has to be known exactly which component has failed.

The objective of the project is to study and analyze of fast fault detection and localization techniques for SDN.

Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

Software Defined Networking (SDN) is a major paradigm in the field of current communication networks. SDN is used as the basis of many new networks although few performance models are available in the literature, and the majority of performance evaluations are based primarily on practical measurements. To fill this gap, we develop an analytical model to assess SDN control plane traffic as well as the occupancy of the flow table of an SDN switch. The contribution of this work is the formulation of the model for the performance-decisive parameters control-plane traffic and flow table occupancy and the application of the model for different data plane traffic characteristics. In the end, there is a discussion about the setting of time-out values for storing flow entries in the switch flow table depending on the traffic characteristics in the data plane. The trade-off between the signaling traffic in the control plane and the occupancy of the flow table is discussed in order to minimize both.

Software Defined Networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks. The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the trade-off between signaling rate and table occupancy. As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this work is threefold. Firstly, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Secondly, we validate the model by means of simulation. Thirdly, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

As the migration towards SDN is in progress, the satisfaction of carrier-grade requirements (fast failure detection, fast reaction, high availability throughout the year) becomes more and more important. The SDN controller ONOS already provides promising mechanisms and tools, but lacks certain capabilities. The task of the project is to enhance ONOS capabilities by implementing the provisioning of backup paths and recovery strategies. <christopher.metter@informatik.uni-wuerzburg.de>

The SDN controller ONOS lacks certain network monitoring capabilities. The task is to develop an ONOS application which utilizes the interfaces provided by ONOS and enableds the active measurement of a predefined set of network metrics.

OFCProbe is a tool to evaluate the performance and behaviour of SDN controllers. Virtual switches generate requests and measure the responses. Today some parts of OFCProbe are outdated. The task is to implement a new version of OFCProbe supporting some of the lastest SDN protocols whilst migrating the architecture of the tool to a more distributed approach, e.g. by using message brokers like ActiveMQ and/or in-memory data grids like Hazelcast. <christopher.metter@informatik.uni-wuerzburg.de>

In the paper 'Analytic Model for SDN Controller Traffic and Switch Table Occupancy' a model has been created and later been verified by simulation. The next step is to test the applicability of the model by measurements. The task is to create a testbed and methods to accomplish this. <christopher.metter@informatik.uni-wuerzburg.de>